The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A motion vector encoding and decoding method conventionally used in a video encoding and decoding field is to perform predictive encoding of a current motion vector with respect to a corresponding motion predicted block by using motion vector of spatially positioned surrounding blocks as predicted motion vectors. In other words, since a motion vector of a current block (hereinafter, referred to as a “current motion vector”) has a close relation with motion vectors of surrounding blocks, a predicted motion vector (PMV) for the current motion vector is first calculated from the motion vectors of the surrounding blocks through a predetermined method and only a differential motion vector (DMV) for the PMV is encoded instead of encoding the current motion vector itself, so as to considerably reduce the quantity of bits to be encoded and thus improve the encoding efficiency. In addition, the motion estimation is performed by using a predetermined search range in which the PMV serves as an initial search point, so that a more similar motion vector than the PMV is determined in a process of the motion estimation. That is, a more accurate motion vector is estimated while a convergence rate in the process of the motion estimation is increased.
Conventionally, the more similar the PMV is to the current vector, the more the encoding efficiency is increased, enabling the most efficient compression in the predictive encoding of the motion vector. Accordingly, through generating multiple predicted motion vector candidates including the motion vectors of temporally or spatial-temporally adjacent blocks or other motion vectors calculated by a method of combining the motion vectors of the spatially adjacent blocks and the temporally adjacent blocks, as well as the motion vectors of the spatially adjacent blocks, as the predicted motion vector candidates and estimating and using a predicted motion vector which is the most appropriate for encoding the current motion vector among the multiple predicted motion vectors, the predictive encoding efficiency can be further improved. Further, estimation of the more accurate motion vector achieved through defining a search range having a center which is a position indicated by each predicted motion vector and performing the motion estimation while using the multiple predicted motion vectors can further improve the encoding efficiency.
However, in order to properly reconstruct the original current motion vector from the differential motion vector predictive-encoded in the decoding process, it is necessary to recognize a PMV used as the predicted motion vector among the finite number of predicted motion vector candidates. To this end, the simplest motion vector encoding method is a method of selecting the most similar predicted motion vector among the finite number of predicted motion vector candidates for the current motion vector and encoding the selected predicted motion vector together with information on the predicted motion vector used for the normal reconstruction of the current motion vector. The aforementioned method may improve the encoding efficiency by utilizing the most similar predicted motion vector to the current motion vector among the motion vectors of the temporal-spatially available adjacent blocks, but additional information on the used predicted motion vector is also required to be encoded, thereby degrading the encoding efficiency.